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Revering tree update (#6561) 

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This commit is contained in:
soufiane-cheouati 2019-04-03 17:27:36 +00:00 committed by Grzegorz Piwowarek
parent 871ee3ccce
commit b7fbf839f9
3 changed files with 142 additions and 143 deletions
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84
algorithms-miscellaneous-2/src/main/java/com/baeldung/algorithms/reversingtree/TreeNode.java
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@ -1,42 +1,42 @@
package com.baeldung.algorithms.reversingtree; package com.baeldung.algorithms.reversingtree;
public class TreeNode { public class TreeNode {
private int value; private int value;
private TreeNode rightChild; private TreeNode rightChild;
private TreeNode leftChild; private TreeNode leftChild;
public int getValue() { public int getValue() {
return value; return value;
} }
public void setValue(int value) { public void setValue(int value) {
this.value = value; this.value = value;
} }
public TreeNode getRightChild() { public TreeNode getRightChild() {
return rightChild; return rightChild;
} }
public void setRightChild(TreeNode rightChild) { public void setRightChild(TreeNode rightChild) {
this.rightChild = rightChild; this.rightChild = rightChild;
} }
public TreeNode getLeftChild() { public TreeNode getLeftChild() {
return leftChild; return leftChild;
} }
public void setLeftChild(TreeNode leftChild) { public void setLeftChild(TreeNode leftChild) {
this.leftChild = leftChild; this.leftChild = leftChild;
} }
public TreeNode(int value, TreeNode rightChild, TreeNode leftChild) { public TreeNode(int value, TreeNode leftChild, TreeNode rightChild) {
this.value = value; this.value = value;
this.rightChild = rightChild; this.rightChild = rightChild;
this.leftChild = leftChild; this.leftChild = leftChild;
} }
public TreeNode(int value) { public TreeNode(int value) {
this.value = value; this.value = value;
} }
} }

121
algorithms-miscellaneous-2/src/main/java/com/baeldung/algorithms/reversingtree/TreeReverser.java
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@ -1,68 +1,53 @@
package com.baeldung.algorithms.reversingtree; package com.baeldung.algorithms.reversingtree;
import java.util.LinkedList; import java.util.LinkedList;
public class TreeReverser { public class TreeReverser {
public TreeNode createBinaryTree() { public void reverseRecursive(TreeNode treeNode) {
if (treeNode == null) {
TreeNode leaf1 = new TreeNode(3); return;
TreeNode leaf2 = new TreeNode(1); }
TreeNode leaf3 = new TreeNode(9);
TreeNode leaf4 = new TreeNode(6); TreeNode temp = treeNode.getLeftChild();
treeNode.setLeftChild(treeNode.getRightChild());
TreeNode nodeLeft = new TreeNode(2, leaf1, leaf2); treeNode.setRightChild(temp);
TreeNode nodeRight = new TreeNode(7, leaf3, leaf4);
reverseRecursive(treeNode.getLeftChild());
TreeNode root = new TreeNode(4, nodeRight, nodeLeft); reverseRecursive(treeNode.getRightChild());
}
return root;
} public void reverseIterative(TreeNode treeNode) {
LinkedList<TreeNode> queue = new LinkedList<TreeNode>();
public void reverseRecursive(TreeNode treeNode) {
if (treeNode == null) { if (treeNode != null) {
return; queue.add(treeNode);
} }
TreeNode temp = treeNode.getLeftChild(); while (!queue.isEmpty()) {
treeNode.setLeftChild(treeNode.getRightChild());
treeNode.setRightChild(temp); TreeNode node = queue.poll();
if (node.getLeftChild() != null)
reverseRecursive(treeNode.getLeftChild()); queue.add(node.getLeftChild());
reverseRecursive(treeNode.getRightChild()); if (node.getRightChild() != null)
} queue.add(node.getRightChild());
public void reverseIterative(TreeNode treeNode) { TreeNode temp = node.getLeftChild();
LinkedList<TreeNode> queue = new LinkedList<TreeNode>(); node.setLeftChild(node.getRightChild());
node.setRightChild(temp);
if (treeNode != null) { }
queue.add(treeNode); }
}
public String toString(TreeNode root) {
while (!queue.isEmpty()) { if (root == null) {
return "";
TreeNode node = queue.poll(); }
if (node.getLeftChild() != null)
queue.add(node.getLeftChild()); StringBuffer buffer = new StringBuffer(String.valueOf(root.getValue())).append(" ");
if (node.getRightChild() != null)
queue.add(node.getRightChild()); buffer.append(toString(root.getLeftChild()));
buffer.append(toString(root.getRightChild()));
TreeNode temp = node.getLeftChild();
node.setLeftChild(node.getRightChild()); return buffer.toString();
node.setRightChild(temp); }
} }
}
public String toString(TreeNode root) {
if (root == null) {
return "";
}
StringBuffer buffer = new StringBuffer(String.valueOf(root.getValue())).append(" ");
buffer.append(toString(root.getLeftChild()));
buffer.append(toString(root.getRightChild()));
return buffer.toString();
}
}

80
algorithms-miscellaneous-2/src/test/java/com/baeldung/algorithms/reversingtree/TreeReverserUnitTest.java
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@ -1,33 +1,47 @@
package com.baeldung.algorithms.reversingtree; package com.baeldung.algorithms.reversingtree;
import static org.junit.jupiter.api.Assertions.assertEquals; import static org.junit.jupiter.api.Assertions.assertEquals;
import org.junit.jupiter.api.Test; import org.junit.jupiter.api.Test;
public class TreeReverserUnitTest { public class TreeReverserUnitTest {
@Test @Test
public void givenTreeWhenReversingRecursivelyThenReversed() { public void givenTreeWhenReversingRecursivelyThenReversed() {
TreeReverser reverser = new TreeReverser(); TreeReverser reverser = new TreeReverser();
TreeNode treeNode = reverser.createBinaryTree(); TreeNode treeNode = createBinaryTree();
reverser.reverseRecursive(treeNode); reverser.reverseRecursive(treeNode);
assertEquals("4 7 9 6 2 3 1", reverser.toString(treeNode) assertEquals("4 7 9 6 2 3 1", reverser.toString(treeNode)
.trim()); .trim());
} }
@Test @Test
public void givenTreeWhenReversingIterativelyThenReversed() { public void givenTreeWhenReversingIterativelyThenReversed() {
TreeReverser reverser = new TreeReverser(); TreeReverser reverser = new TreeReverser();
TreeNode treeNode = reverser.createBinaryTree(); TreeNode treeNode = createBinaryTree();
reverser.reverseIterative(treeNode); reverser.reverseIterative(treeNode);
assertEquals("4 7 9 6 2 3 1", reverser.toString(treeNode) assertEquals("4 7 9 6 2 3 1", reverser.toString(treeNode)
.trim()); .trim());
} }
} private TreeNode createBinaryTree() {
TreeNode leaf1 = new TreeNode(1);
TreeNode leaf2 = new TreeNode(3);
TreeNode leaf3 = new TreeNode(6);
TreeNode leaf4 = new TreeNode(9);
TreeNode nodeRight = new TreeNode(7, leaf3, leaf4);
TreeNode nodeLeft = new TreeNode(2, leaf1, leaf2);
TreeNode root = new TreeNode(4, nodeLeft, nodeRight);
return root;
}
}